From: James Morse <james.morse@arm.com>
To: Ben Horgan <ben.horgan@arm.com>
Cc: reinette.chatre@intel.com, fenghuay@nvidia.com,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, dave.martin@arm.com,
andre.przywara@arm.com, Gavin Shan <gshan@redhat.com>
Subject: Re: [PATCH v2 10/12] arm_mpam: Don't loop forever if there is the maximum possible amount of PARTIDs
Date: Fri, 2 Oct 2026 16:18:03 +0100 [thread overview]
Message-ID: <01e3c08b-8127-46ac-9d88-0e289f7ce2c1@arm.com> (raw)
In-Reply-To: <20260917145617.2202986-11-ben.horgan@arm.com>
Hi Ben,
On 17/09/2026 15:56, Ben Horgan wrote:
> On a theoretical platform with the maximum possible number of usable
> PARTIDs, 0XFFFF, the loops iterating over PARTID in mpam_reset_ris() and
> mpam_reprogram_ris() will never reach their termination condition leading
> to a system hang when register the cpu hotplug handlers when MPAM is
> enabling.
>
> Fix these loops.
Ha! MPAM's mixture of num/max fields is really annoying.
Looks like we never loop over the PMG field.
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index cdc2d9d19e19..10fc5168699b 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -1754,7 +1754,7 @@ static int mpam_save_mbwu_state(void *arg)
> */
> static int mpam_reset_ris(void *arg)
> {
> - u16 partid, partid_max;
> + u16 partid_max;
> struct mpam_config reset_cfg = {};
> struct mpam_msc_ris *ris = arg;
>
> @@ -1764,7 +1764,7 @@ static int mpam_reset_ris(void *arg)
> spin_lock(&partid_max_lock);
> partid_max = mpam_partid_max;
> spin_unlock(&partid_max_lock);
> - for (partid = 0; partid <= partid_max; partid++)
> + for (u32 partid = 0; partid <= partid_max; partid++)
> mpam_reprogram_ris_partid(ris, partid, &reset_cfg);
>
> return 0;
> @@ -1811,7 +1811,6 @@ static int __write_config(void *arg)
>
> static void mpam_reprogram_msc(struct mpam_msc *msc)
> {
> - u16 partid;
> bool reset;
> struct mpam_config *cfg;
> struct mpam_msc_ris *ris;
> @@ -1835,7 +1834,7 @@ static void mpam_reprogram_msc(struct mpam_msc *msc)
> arg.comp = ris->vmsc->comp;
> arg.ris = ris;
> reset = true;
> - for (partid = 0; partid <= mpam_partid_max; partid++) {
> + for (u32 partid = 0; partid <= mpam_partid_max; partid++) {
> cfg = &ris->vmsc->comp->cfg[partid];
> if (!bitmap_empty(cfg->features, MPAM_FEATURE_LAST))
> reset = false;
Reviewed-by: James Morse <james.morse@arm.com>
Thanks,
James
next prev parent reply other threads:[~2026-10-02 15:18 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 14:56 [PATCH v2 00/12] arm_mpam: minor fixes at v7.2 Ben Horgan
2026-09-17 14:56 ` [PATCH v2 01/12] arm_mpam: Move MPAMF_ECR write helpers to allow reuse Ben Horgan
2026-09-22 5:41 ` Gavin Shan
2026-10-02 14:58 ` James Morse
2026-09-17 14:56 ` [PATCH v2 02/12] arm_mpam: Restore the error interrupt enable from mpam_cpu_online() Ben Horgan
2026-09-22 5:42 ` Gavin Shan
2026-10-02 15:00 ` James Morse
2026-09-17 14:56 ` [PATCH v2 03/12] arm_mpam: Set mpam_feat_msmon_mbwu_31counter when there are bandwidth counters Ben Horgan
2026-09-22 5:42 ` Gavin Shan
2026-10-02 15:01 ` James Morse
2026-09-17 14:56 ` [PATCH v2 04/12] arm_mpam: Add missing mon_sel locking in MBWU save and restore Ben Horgan
2026-10-02 15:01 ` James Morse
2026-10-02 15:28 ` Ben Horgan
2026-09-17 14:56 ` [PATCH v2 05/12] arm_mpam: Ensure MBWU counters are reset on restore Ben Horgan
2026-09-22 5:43 ` Gavin Shan
2026-10-02 15:13 ` James Morse
2026-10-02 15:24 ` Ben Horgan
2026-09-17 14:56 ` [PATCH v2 06/12] arm_mpam: Use __ris_msmon_read() for saving MBWU state Ben Horgan
2026-10-02 15:15 ` James Morse
2026-10-02 15:22 ` Ben Horgan
2026-10-02 16:21 ` James Morse
2026-09-17 14:56 ` [PATCH v2 07/12] arm_mpam: Initialize all of struct mon_read in mpam_restore_mbwu_state() Ben Horgan
2026-10-02 15:15 ` James Morse
2026-09-17 14:56 ` [PATCH v2 08/12] arm_mpam: resctrl: Correct check that existing class is L3 Ben Horgan
2026-09-22 5:43 ` Gavin Shan
2026-10-02 15:15 ` James Morse
2026-09-17 14:56 ` [PATCH v2 09/12] arm_mpam: resctrl: Make read_mon_cdp_safe() self consistent Ben Horgan
2026-09-22 5:44 ` Gavin Shan
2026-10-02 15:17 ` James Morse
2026-09-17 14:56 ` [PATCH v2 10/12] arm_mpam: Don't loop forever if there is the maximum possible amount of PARTIDs Ben Horgan
2026-09-22 5:44 ` Gavin Shan
2026-10-02 15:18 ` James Morse [this message]
2026-09-17 14:56 ` [PATCH v2 11/12] arm_mpam: Switch to kvzmalloc_objs() for allocation of component cfg Ben Horgan
2026-09-22 5:45 ` Gavin Shan
2026-10-02 15:18 ` James Morse
2026-09-17 14:56 ` [PATCH v2 12/12] arm_mpam: resctrl: Don't stop early when tearing down a class Ben Horgan
2026-09-22 5:45 ` Gavin Shan
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